Magnetic tape cartridge

ABSTRACT

A magnetic tape cartridge has a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape. The leader pin is provided at its opposite ends with engagement portions which are brought into engagement with a tape drawing mechanism of a recording and reproducing system when the magnetic tape cartridge is loaded in the recording and reproducing system. The end face of each engagement portion is provided with a recess at which the tape drawing mechanism chucks the leader pin.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a magnetic tape cartridge, and more particularly to a magnetic tape cartridge comprising a cartridge casing and a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation.

[0003] 2. Description of the Related Art

[0004] There has been known a single reel magnetic tape cartridge comprising a flat cartridge casing which is formed by upper and lower shell halves and is substantially square in shape and a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation. Such a single reel magnetic tape cartridge has been used for retaining data of a computer or the like. A tape outlet opening is formed in a side wall of the cartridge casing and when the magnetic tape cartridge is used, i.e., when the magnetic tape cartridge is loaded in a recording and reproducing system as, for instance, an external storage for a computer and information is to be recorded on the magnetic tape or information recorded on the magnetic tape is to be read, the magnetic tape wound around the reel is drawn out through the tape outlet opening.

[0005] In such a magnetic tape cartridge of one type, a leader block is fixed to the leading end of a leader tape which is connected to the magnetic tape and when the magnetic tape cartridge is not used, the magnetic tape is fully wound around the reel with the leader block fitted in the tape outlet opening to close the tape outlet opening. In the case of the magnetic tape cartridge of this type, when the magnetic tape cartridge is loaded in the recording and reproducing system, a drive means in the recording and reproducing system engages with engagement teeth on the reel exposed outside at the central portion of the lower casing half and a tape drawing mechanism in the recording and reproducing system chucks the leader block and draws the magnetic tape outside the cartridge casing into a tape running path of the recording and reproducing system.

[0006] In another type, the tape outlet opening is closed and opened by a lid which is rotatable between a closing position where it closes the tape outlet opening and an opening position where it opens the tape outlet opening, the lid being urged by a spring toward the closing position. A hook member is fixed to the leading end of a leader tape which is connected to the magnetic tape and when the magnetic tape cartridge is not used, the magnetic tape is fully wound around the reel with the hook member retracted inside the tape outlet opening and the lid held in the closing position. In the case of the magnetic tape cartridge of this type, when the magnetic tape cartridge is loaded in the recording and reproducing system, a drive means in the recording and reproducing system engages with engagement teeth on the reel exposed outside at the central portion of the lower casing half and a tape drawing mechanism in the recording and reproducing system moves the lid to the opening position, chucks the hook member and draws the magnetic tape outside the cartridge casing into a tape running path of the recording and reproducing system.

[0007] Recently, the recording and reproducing system (will be referred to as “tape drive system” hereinbelow) comes to require employment of a leader pin about 3 mm thick in place of the leader block or the hook member. However attempts at meeting such requirement have encountered a difficulty that it is difficult for the tape drawing mechanism in the tape drive system to surely chuck such a thin leader pin.

SUMMARY OF THE INVENTION

[0008] In view of the foregoing observations and description, the primary object of the present invention is to provide a magnetic tape cartridge which is provided with a leader pin which can be surely chucked by the tape drawing mechanism in the tape drive system.

[0009] In the following description, a term “a magnetic tape” sometimes means “a magnetic tape with a leader tape connected thereto”.

[0010] The magnetic tape cartridge in accordance with the present invention comprises a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation, and a leader pin fixed to the leading end portion of the magnetic tape and is characterized in that the leader pin is provided at its opposite ends with engagement portions which are brought into engagement with a tape drawing mechanism of a recording and reproducing system when the magnetic tape cartridge is loaded in the recording and reproducing system, and the end face of each engagement portion is provided with a recess at which the tape drawing mechanism chucks the leader pin.

[0011] With this arrangement, though simple in structure, the tape drawing mechanism of the recording and reproducing system can surely chuck the leader pin.

[0012] It is preferred that each engagement portion be provided with a smaller diameter portion and a flange on the outer side of the smaller diameter portion and the recess be formed on the outer end face of the flange at the center thereof.

[0013] For example, the leader pin may comprise a body portion provided with the aforesaid engagement portions at its opposite ends and a clamp member which is press-fitted on the body portion sideways with the leading end portion of the magnetic tape sandwiched therebetween.

[0014] With this arrangement, the leader pin can be easily fixed to the leading end portion of the magnetic tape.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a perspective view showing a magnetic tape cartridge in accordance with an embodiment of the present invention with the slide door closed,

[0016]FIG. 2 is a perspective view showing the magnetic tape cartridge with the slide door opened,

[0017]FIG. 3 is a side view partly cutaway showing a basic appearance of the leader pin,

[0018]FIG. 4A is an exploded perspective view of a first specific example of the leader pin,

[0019]FIG. 4B is a cross-sectional view of the leader pin,

[0020]FIG. 5 is an exploded perspective view of a second specific example of the leader pin,

[0021]FIG. 6A is a cross-sectional view of the second specific example of the leader pin in an assembled stated,

[0022]FIG. 6B is a view similar to FIG. 6A but showing a modification of the second example,

[0023]FIG. 6C is fragmentary cross-sectional view for illustrating another modification of the second example,

[0024]FIG. 7 is an exploded perspective view of still another modification of the second example,

[0025]FIG. 8 is an exploded perspective view of a third specific example of the leader pin,

[0026]FIG. 9 is an exploded perspective view of a fourth specific example of the leader pin,

[0027]FIG. 10 is an exploded perspective view of a fifth specific example of the leader pin,

[0028]FIG. 11A is an exploded cross-sectional view of the fifth example,

[0029]FIG. 11B is a cross-sectional view of the fifth example in an assembled state,

[0030]FIGS. 12A and 12B are schematic cross-sectional views for illustrating a sixth specific example of the leader pin,

[0031]FIGS. 13A and 13B are schematic cross-sectional views for illustrating a modification of the sixth specific example,

[0032]FIGS. 14A and 14B are schematic cross-sectional views for illustrating another modification of the sixth specific example,

[0033]FIG. 15 is a schematic side view of a seventh specific example of the leader pin,

[0034]FIGS. 16A and 16B are cross-sectional views taken along line XVI-XVI in FIG. 15 before and after clamping the magnetic tape,

[0035]FIGS. 17A and 17B are views similar to FIGS. 16A and 16B but showing a modification of the seventh example,

[0036]FIG. 18A is a fragmentary perspective view of an eighth specific example of the leader pin,

[0037]FIG. 18B is a cross-sectional view of the eighth example,

[0038]FIG. 18C is a view similar to FIG. 18B but showing a modification of the eighth example,

[0039]FIG. 18D is a cross-sectional view showing the leading end portion of the magnetic tape wound around the leader pin,

[0040]FIG. 19A is fragmentary perspective view of another modification of the eighth example,

[0041]FIG. 19B is a cross-sectional view of the modification,

[0042]FIG. 19C is a view similar to FIG. 19B but showing a still another modification of the eighth example,

[0043]FIG. 20 is a side view of a ninth example of the leader pin,

[0044]FIGS. 21A to 21C are cross-sectional views taken along line XXI-XXI in FIG. 20 showing variations of manner of connecting the leader tape to the leader pin,

[0045]FIG. 21D is a vertical cross-sectional view of FIG. 20 showing another variation of manner of connecting the leader tape to the leader pin,

[0046]FIG. 22 is a side view showing a modification of the ninth example,

[0047]FIG. 23 is an exploded side view of a tenth specific example of the leader pin,

[0048]FIG. 24A is a cross-sectional view taken along line A-A in FIG. 23,

[0049]FIG. 24B is a cross-sectional view taken along line B-B in FIG. 23,

[0050]FIG. 25A is a vertical cross-sectional view of a eleventh example of the leader pin,

[0051]FIGS. 25B and 25C are views similar to FIG. 25A but showing modifications of the eleventh example,

[0052]FIG. 26 is a cross-sectional view taken along line XXVI-XXVI in FIG. 25A,

[0053]FIG. 27 is a view for illustrating the dimensions of important parts of the eleventh example,

[0054]FIG. 28 is a vertical cross-sectional view of a twelfth example of the leader pin,

[0055]FIG. 29 is a perspective view of a thirteenth example of the leader pin,

[0056]FIG. 30 is a perspective view of the pin half in the thirteenth example,

[0057]FIG. 31 is an exploded side view of the leader pin of the thirteenth example,

[0058]FIG. 32 shows cross-sections of the thirteenth example taken along different planes,

[0059]FIG. 33 is a cross-sectional view for illustrating a modification of the thirteenth example,

[0060]FIG. 34 is an exploded side view of a fourteenth specific example of the leader pin,

[0061]FIGS. 35A and 35B are cross-sectional views taken along lines A-A and B-B in FIG. 34,

[0062]FIGS. 36A to 36C are cross-sectional views for illustrating tape clamping operation of the fourteenth example,

[0063]FIG. 37 is an exploded perspective view of a fifteenth specific example of the leader pin,

[0064]FIG. 38 is a perspective view of the fifteenth example in an assembled state,

[0065]FIG. 39 is a cross-sectional view of the fifteenth example,

[0066]FIG. 40 is an exploded perspective view of a sixteenth specific example of the leader pin,

[0067]FIGS. 41A and 41B are views showing different manners of connecting the leader tape to the magnetic tape,

[0068]FIGS. 42A to 42C are views showing different manners of clamping the leading end portion magnetic tape by the leader pin of the preceding examples,

[0069]FIG. 43 is a perspective view of a modification of the clamp member,

[0070]FIG. 44 is view for illustrating an example of the manner for press-fitting the clamp member shown in FIG. 43 on the pin body,

[0071]FIG. 45 is a view for illustrating a method of bonding the magnetic tape to the leader pin by use of hot-melt adhesive tape,

[0072]FIG. 46 is a perspective view of a leader pin of another example,

[0073]FIG. 47A is a fragmentary perspective view of a leader pin of still another example,

[0074]FIGS. 47B and 47C are fragmentary perspective views showing modifications of the leader pin,

[0075]FIGS. 48 and 49 are perspective views showing the manner of forming a leader pin-magnetic tape assembly,

[0076]FIG. 50 is a transverse cross-sectional view of FIG. 49,

[0077]FIG. 51 is a fragmentary cross-sectional view showing the inside of the magnetic tape cartridge near the tape outlet opening 2,

[0078]FIG. 52 is a cross-sectional view taken along line X-X in FIG. 41,

[0079]FIG. 52 is a fragmentary perspective view showing a modification of the guide surface,

[0080]FIG. 53 is a fragmentary perspective view showing another modification of the guide surface,

[0081]FIG. 54 is a fragmentary perspective view showing still another modification of the guide surface,

[0082]FIG. 55A is a fragmentary cross-sectional view showing still another modification of the guide surface, and

[0083]FIG. 55B is a fragmentary cross-sectional view showing still another modification of the guide surface.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0084] In FIGS. 1 and 2, a magnetic tape cartridge in accordance with an embodiment of the present invention comprises a cartridge casing 1 formed by upper and lower casing halves 1 a and 1 b and a single reel (not shown) around which a magnetic tape is wound and which is supported for rotation in the cartridge casing 1. A tape outlet opening 2 through which the magnetic tape is drawn out is formed in one end face of the cartridge casing 1 near a corner thereof. A slide door 3 for opening and closing the tape outlet opening 2 is mounted in the cartridge casing 1 to be slidable back and forth between a closing position where it closes the tape outlet opening 2 and opening position where it opens the same. The slide door 3 is urged toward the closing position by a spring not shown disposed between a side face of the cartridge casing 1 and the slide door 3.

[0085] As shown in FIG. 2, a leader pin 4 fixed to the leading end of the magnetic tape is held inside the tape outlet opening 2. When the magnetic tape cartridge is loaded in a tape drive system, a reel drive means of the tape drive system is brought into engagement with engagement teeth (not shown) on the reel which is exposed in the bottom face of the cartridge casing 1 at the center thereof and a tape drawing mechanism of the tape drive system pushes the front end face 3 a of the slide door 3 to open the slide door 3. Further the tape drawing mechanism chucks the leader pin 4 and pulls the leader pin 4 into the system, whereby the magnetic tape is set in the tape drive system so that data can be recorded on or read out from the magnetic tape.

[0086] A knob 5 for inhibiting erasure and write projects outside in one side face of the cartridge casing 1.

[0087] As shown in FIG. 3, the leader pin 4 basically comprises a main portion 11 at which the leading end portion of the magnetic tape is clamped, a pair of small diameter portions 12 which extend from the upper and lower end of the main portion 11 and a pair of flanges 13 which are formed on the outside of the small diameter portions 12. The small diameter portions 12 form an engagement portions which are brought into engagement with the tape drawing mechanism of the tape drive system. Each of the flanges 13 is provided at the center of its end face with a conical recess 13 a at which the tape drawing mechanism chucks the leader pin 4. The main portion 11 is substantially equal in length to the width (½ inches) of the magnetic tape.

[0088] Examples of the specific structure of the leader pin 4 will be described, hereinbelow. FIG. 4A is an exploded perspective view of the leader pin 4 of a first example and FIG. 4B is a cross-sectional view of the same. As shown in FIGS. 4A and 4B, the leader pin 4 of the first example comprises a body portion 15 of metal or hard plastic and a clamp member 16 of metal or hard plastic. The body portion 15 has a relatively thick middle portion, a pair of inner flanges 14 on opposite ends of the middle portion, a pair of small diameter portions 12 on the upper and lower sides of the inner flanges 14 and a pair of outer flanges 13 on the upper and lower sides of the small diameter portions 12. The clamp member 16 has an axial hole which extends over the entire length of the clamp member 16 and opens outward through a slit 16 a extending over the entire length of the clamp member 16. The clamp member 16 is press-fitted on the middle portion of the body portion 15 between the inner flanges 14 through the slit 16 a with the leading end portion of the magnetic tape 10 pinched between the inner wall surface of the axial hole of the clamp member 16 and the outer surface of the middle portion of the body portion 15 a, whereby the leading end portion of the magnetic tape 10 is fixed to the leader pin 4.

[0089] With this arrangement, the leading end portion of the magnetic tape 10 can be easily and surely fixed to the leader pin 4, and the conical recesses on the outer flanges 13 makes it feasible for the tape drawing mechanism of the tape drive system to surely chuck the leader pin 4.

[0090] The clamp member 16 may be formed of shape memory alloy instead of elastic material. In this case, the clamp member 16 is heated and fitted on the middle portion of the body portion 15 between the inner flanges 14 through the slit 16 a with the leading end portion of the magnetic tape 10 pinched between the inner wall surface of the axial hole of the clamp member 16 and the outer surface of the middle portion of the body portion 15. Thereafter the clamp member 16 is cooled to normal temperatures, whereby the axial hole of the clamp member 16 is reduced in its inner diameter under shape memory effect and the leading end it portion of the magnetic tape 10 is clamped on the outer surface of the body portion 15.

[0091] Examples of the specific structures of the leader pin which are provided with a tape positioning means for positioning the leading end portion of the magnetic tape 10 with respect to the leader pin will be described, hereinbelow.

[0092]FIG. 5 shows a leader pin of a second example. As shown in FIG. 5, the leader pin of this example comprises a pin body 114 of metal or hard plastic. The pin body 114 has a pair of flanges 13 on opposite ends thereof and a shaft portion 115 which extends between the flanges 113 and is substantially uniform in diameter. A resilient clamp member 116 which is larger than the shaft portion 115 in outer diameter and is smaller than the shaft portion 115 in length is press-fitted on the middle portion of the shaft portion 115. When the clamp member 116 is press-fitted on the middle portion of the shaft portion 115, the small diameter portions 12 (FIG. 3) are formed on opposite sides of the clamp member 116. A groove 115 a is formed on the shaft portion 115 to extend in the longitudinal direction of the pin body 114.

[0093] The clamp member 116 has an axial hole which extends over the entire length of the clamp member 116 and opens outward through a slit 116 a extending over the entire length of the clamp member 116. A flange 117 is formed on one edge of the slit 116 a of the clamp member 116 to project toward the longitudinal axis of the clamp member 116.

[0094] The clamp member 116 is press-fitted on the shaft portion 115 of the pin body 114 with the flange 117 engaged with the groove 115 a as shown in FIG. 6A. By bringing the leading edge of the magnetic tape 10 into abutment against the inner surface 117 a of the flange 117 when clamping the leading end portion of the magnetic tape 10 between the pin body 114 and the clamp member 116, the magnetic tape 10 can be easily positioned with respect to the leader pin 4. It is preferred that the clamp member 116 be formed of deposition hardened steel such as SUS631 in order to increase resiliency of the clamp member 116.

[0095] In the case of this example, since the shaft portion 115 of the pin body 114 is circular in cross-section, the main portion 11 (FIG. 3) formed by fitting the clamp member 116 on the shaft portion 115 cannot be circular in cross-section. When the shaft portion 115 is in such a shape that forms circular cross-section together with the clamp member 116 as shown in FIG. 6B, the main portion 11 formed by fitting the clamp member 116 on the shaft portion 115 can be circular in cross-section.

[0096] Further by forming a groove 117 b on the base of the inner surface 117 a of the flange 117 and inserting the leading end of the magnetic tape 10 in the groove 117 b as shown in FIG. 6C, positioning of the leading end portion of the magnetic tape 10 with respect to the leader pin can be more facilitated.

[0097] Further when a short groove 115 b is formed on the shaft portion 115 in perpendicular to the groove 115 a to be connected to the groove 115 a at one end thereof and a projection 116 b is formed on the clamp member 116 at one end as shown in FIG. 7 so that the projection 116 b is received in the short groove 115 b when the clamp member 116 is fitted on the pin body 114, positioning of the magnetic tape 10 with respect to the leader pin in the axial direction thereof can be facilitated by bringing a side edge of the magnetic tape 10 into abutment against the projection 116 b.

[0098]FIG. 8 shows a leader pin of a third embodiment in which positioning of the magnetic tape 10 with respect to the leader pin in the axial direction thereof is facilitated. The leader pin of this example differs from that of the second example in that the shaft portion 115 is not provided with the groove 115 a and accordingly the clamp member 116 is not provided with the flange 117, and instead the clamp member 116 is provided with a pair of arcuate shoulders 116 c extending from the slit 116 a on opposite ends of the clamp member 116. The magnetic tape 10 is positioned with respect to the leader pin in the axial direction of the leader pin, i.e., in the transverse direction of the magnetic tape 10, by bringing the side edges of the magnetic tape 10 into abutment against the shoulders 116 c.

[0099] In the fourth example shown in FIG. 9, the outer diameter of the shaft portion 115 is slightly smaller than that of the small diameter portions 12 and shoulders 115 c are formed between the shaft portion 115 and each of the small diameter portion 12. The magnetic tape 10 is positioned with respect to the leader pin in the axial direction of the leader pin by use of the shoulder 115 c.

[0100] In the fifth example shown in FIG. 10, the pin body 114 is the same as that shown in FIG. 8 but the magnetic tape 10 is fixed to the leader pin by a pair of split clamp members 118 of plastic. That is, the clamp members 118 are semi-cylindrical in shape and are fixed together by adhesive with the pin body 114 and the leading end portion of the magnetic tape 10 intervening therebetween as shown in FIGS. 11A and 11B. The tip of the leading end portion of the magnetic tape 10 projecting outside the clamp members 118 is cut after bonding the clamp members 118. The leader pin of this example is easy to manufacture and is advantageous in that positioning of the magnetic tape 10 is easy.

[0101] As a sixth example of the leader pin and its modifications, the main portion 11 may be formed of pair of members 119A and 119B which are brought into resilient engagement with each other with the leading portion of the magnetic tape 10 pinched therebetween as shown in FIGS. 12A and 12B, 13A and 13B and 14A and 14B, respectively. In the examples shown in FIGS. 12A and 12B and 13A and 13B, the members 119A and 119B are hinged to each other at H and the example shown in FIGS. 14A and 14B, the members 119A and 119B are separate from each other.

[0102] In the seventh example shown in FIGS. 15, 16A and 16B, the main portion 11 of the leader pin 4 is formed with a slit 120 diametrically through the main portion 11. The slit 120 is flared in cross-section from the center of the main portion 11 toward the opening 120 a on the side opposite to the side from which the leading end portion of the magnetic tape 10 is inserted into the slit 120. After the magnetic tape 10 is inserted into the slit 120, a wedge-shaped clamp member 121 is press-fitted in the slit 120 from the opening 120 a, thereby clamping the magnetic tape 10 on the main portion 11 as shown in FIG. 16A. This example is advantageous in that the leader pin 4 can be simple in structure. It is preferred that the wedge-shaped clamp member 121 be substantially the same in the radius of curvature of the outer surface thereof as that of the leader pin 4.

[0103] In a modification of the seventh example shown in FIGS. 17A and 17B, a bifurcated wedge-shaped clamp member 123 is used. The clamp member 123 is provided with a pair of hooks 123 a on the tips of the arms and the main portion 11 of the leader pin 4 is provided with a slit 122 which is flared in cross-section from the center of the main portion 11 toward the opening 122 a on the side opposite to the side from which the leading end portion of the magnetic tape 10 is inserted into the slit 122 and is provided with a pair of shoulders 122 b. When the clamp member 123 is press-fitted in the slit 122 from the opening 122 a, the arms of the member 123 is once resiliently bent toward each other and then spring away from each other into engagement with the shoulders 122 b, whereby the clamp member 123 and the magnetic tape 10 are prevented from being disengaged from the slit 122.

[0104] In the eighth example shown in FIGS. 18A to 18D, a slit 124 is formed in the main portion 11 of the leader pin 4 and the leading end portion of the magnetic tape 10 is inserted into the slit 124. The magnetic tape 10 is held on the leader pin 4 by winding the magnetic tape 10 around the main portion 11 with the leading end portion inserted into the slit 124 as shown in FIG. 18D. In this example, the slit 124 may extend either through the main portion 11 as shown in FIG. 18B or not through the main portion 11 as shown in FIG. 18C.

[0105] The slit 124 may reach the flanges 13 as shown in FIGS. 19A and 19B so that the slit 124 can be easily formed, for instance, by wire cutting. Further the slit 124 may be formed so that a thin portion 11 a is formed on the outer side of the slit 124 as shown in FIG. 19C and the magnetic tape 10 may be held in the slit 124 under the resiliency of the thin portion 11 a.

[0106] In the ninth example shown in FIG. 20, the magnetic tape 10 is connected to a temperature-resistant connecting sheet 125. That is, the leader pin 4 is formed by plastic molding and when the leader pin 4 is molded, the connecting sheet 125 is inserted so that the connecting sheet 125 is projected from the leader pin 4 as shown in FIG. 21A. The connecting sheet 125 is substantially equal in width to the magnetic tape 10 and the leading end portion of the magnetic tape 10 is connected to the connecting sheet 125, for instance, by use of splicing tape 126.

[0107] By forming a bent portion 125 a or 125 b in the end portion of the connecting tape 125 as shown in FIG. 21B or 21C or forming a small opening 125 c in the end portion of the connecting tape 125 as shown in FIG. 21D, bonding strength of the connecting sheet 125 to the leader pin 4 can be increased.

[0108] The magnetic tape 10 may be bonded to the connecting sheet 125 by heat-sensitive adhesive as shown in FIG. 22.

[0109] In the tenth example shown in FIG. 23, a leader tape 128 such as photographic film which has suitable strength and rigidity is connected to the leading end of the magnetic tape 10, for instance, by use of splicing tape 126 and a slit 129 is formed in the leader pin 4. The leader tape 128 is provided with a pair of engagement holes 128 a on upper and lower edges thereof.

[0110] Further as shown in FIGS. 24A and 24B, a pair of engagement projections 130 projects from one side wall of the slit 129 and a retainer projection 131 projects from the other side wall of the slit 129 at the middle between the engagement projections 130. The leader tape 128 is inserted into the slit 129 and the engagement holes 128 a are brought into engagement with the engagement projections 130 as shown in FIG. 24A. The retainer projection 131 pushes the leader tape 128 toward the engagement projections 130, thereby preventing the engagement holes 128 a from being disengaged from the engagement projections 130 as shown in FIG. 24B.

[0111] This example is advantageous in that the leader tape 128 can be easily connected to the leader pin 4.

[0112] In the eleventh example shown in FIGS. 25A to 25C, the pin body 114 is provided with a pair of inner flanges 132 which separates the shaft portion 115 from the small diameter portions 12 and a clamp member 116 which is C-shaped in cross-section is press-fitted on the shaft portion 115 between the inner flanges 132 as shown in FIG. 26. The inner flanges 132 are spaced from each other by a distance substantially equal to the width of the magnetic tape 10 and are used to position the magnetic tape 10 with respect to the leader pin 4.

[0113] When the distance between the outer surface of the small diameter portion 12 and the outer surface of the outer flange 13 is represented by h, the distance between the outer surface of the shaft portion 115 and the outer surface of the inner flange 13 is represented by a, and the distance between the outer surface of the small diameter portion 12 and the outer surface of the inner flange 132 is represented by b as shown in FIG. 27, at least one of a and b is not larger than 2 h/3 in any one of the leader pins shown in FIGS. 25A to 25C.

[0114] In the leader pin shown in FIG. 25A, the outer diameter of the shaft portion 115 is equal to that of the small diameter portion 12 and a=b≦2 h/3. The clamp member 116 has a length slightly smaller than the distance between the inner flanges 132.

[0115] In the leader pin shown in FIG. 25B, the outer diameter of the shaft portion 115 is also equal to that of the small diameter portion 12 but the clamp member 116 has a length substantially equal to the distance between the inner flanges 132. The clamp member 116 is provided with an annular recess 133 at each end face thereof and the inner flanges 132 are received in the recesses 133 when the clamp member 116 is fitted on the pin body 114.

[0116] In the leader pin shown in FIG. 25C, the diameter of the inner flanges 132 is substantially equal to that of the outer flanges 13 and accordingly b=h. However since the shaft portion 115 is larger in diameter than the small diameter portions 12, a<2 h/3. Accordingly, the clamp member 116 is thinner than that employed in the leader pin shown in FIG. 25A or 25B and is formed of hoop (stainless steel or the like is preferred in view of resistance to corrosion and/or hardness to magnetize.

[0117] Thus in the leader pins of this example, positioning of the magnetic tape 10 and the clamp member 116 is facilitated by virtue of the inner flanges 132 and at the same time even if the inner flanges 132 are small in thickness (about 0.4 to 0.6 mm), there arises no problem with respect to the strength and/or productivity of the leader pins since the height of the inner flanges 132 from the outer surface of the shaft portion 115 and/or the small diameter portions 12 satisfies the aforesaid condition.

[0118] In the twelfth example shown in FIG. 28, a pair of annular recesses 134 are formed on the pin body 112 between the shaft portion 115 and the small diameter portions 12, and a pair of annular protrusions 135 are formed on the inner peripheral surfaces of the clamp member 116 at the ends thereof. The annular protrusions 135 are received in the annular recesses 134 on the pin body 114 when the clamp member 116 is fitted on the pin body 114.

[0119] With this arrangement, the clamp member 116 can be accurately positioned with respect to the pin body 114. Further the magnetic tape 10 can be accurately positioned with respect to the leader pin 4 by virtue of the annular protrusions 135 on the clamp member 116. Further the annular protrusions 135 protects the side edges of the magnetic tape 10 when the tape drawing mechanism of the tape drive system is brought into engagement with the small diameter portions 12. Further since the inner flanges are not used, problems which arise when inner flanges small in thickness and large in height are used can be avoided.

[0120] In the thirteenth example shown in FIGS. 29 to 32, the leader pin 4 is formed by left and right pin halves 4L and 4R which are butted together along a plane P including the longitudinal axis of the leader pin 4.

[0121] As shown in FIG. 30, the left pin half 4L has an elongated groove 136 formed on the plane P to extend in the longitudinal direction of the pin half 4L and an elongated protrusion 137 formed on the plane P to extend in the longitudinal direction of the pin half 4L in a position symmetrical to the position of the groove 136 about the center line. A through hole 138 is formed in the upper flange 13 to extend from the plane P to the outer surface of the flange 13 while an engagement projection 139 is formed on the lower flange 13 to project from the plane P. The through hole 138 is provided with a pair of engagement shoulders 138 a and the engagement projection 139 comprises a pair of resilient engagement pieces 139 a each having a hook portion 139 a projecting outward.

[0122] The right pin half 4R is identical to the left pin half 4L except that the right pin half 4R is positioned upside down relative to the left pin half 4L. That is, when the left and right pin halves 4L and 4R are butted together with the leading end portion of the magnetic tape 10 intervening therebetween, the engagement projection 138 a on each of the left and right pin halves 4L and 4R is inserted into the through hole 138 of the other pin half, and the protrusion 137 of each of the left and right pin halves 4L and 4R is inserted into the grooves 136 of the other pin half as shown in FIG. 32. The hook portions 139 b of the engagement projections 139 a are engaged with the engagement shoulders 138 a of the through holes 138 and hold together the left and right pin halves 4L and 4R with the magnetic tape 10 pinched therebetween. It is preferred that the radius of curvature of the end faces of the engagement pieces 139 a be equal to that of the outer surfaces of the flanges 13 so that the outer surfaces of the flanges 13 formed by the pin halves 4L and 4R become smooth.

[0123] Further the magnetic tape 10 is firmly clamped between the left and right pin halves 4L and 4R by virtue of the engagement between the grooves 136 and the protrusions 137.

[0124] This example is advantageous from the viewpoint of productivity in that the leader pin can be formed by two identical members and assembly of the leader pin and clamp of the magnetic tape 10 can be effected at one time by simply pressing the left and right halves 4L and 4R against each other.

[0125] Instead of fixing the pin halves 4L and 4R to each other by engagement of the flanges 13 as in the thirteenth example, the pin halves 4L and 4R may be fixed to each other by fitting a projection 142 on one of the flanges in a recess 141 on the other flange as shown in FIG. 33 and bonding the pin halves 4L and 4R by adhesive. This arrangement is advantageous in that no hole is formed on the outer surfaces of the flanges.

[0126] In the fourteenth example shown in FIGS. 34, 35A, 35B and 36A to 36C, the leader pin 4 is formed by first and second members 4M and 4S. The first member 4M is provided with a main portion 11 in the form of a hollow cylindrical member having an axial hole 143 and a slit 144 communicated with the axial hole 143. One of the small diameter portions 12 and one of the flanges 13 are formed on the upper end of the main portion 11 and the axial hole 143 opens in the lower end face of the main portion 11 which is flat. The second member 4S has a shaft portion 145 which is inserted for rotation into the axial hole 143 of the first member 4M and the other small diameter portion 12 and the other flange 13 are formed on the lower end face of the shaft portion 145. The shaft portion 145 is semi-circular in cross-section and has a flat side surface 145 a.

[0127] When the leader pin 4 is assembled, the shaft portion 145 of the second member 4S is inserted into the axial hole 143 of the first member 4M with the flat surface 145 a faced so that a space 146 communicated with the slit 144 is formed inside the axial hole 143 as shown in FIG. 36A. Then the leading end portion of the magnetic tape 10 is inserted into the space 146 through the slit 144 as shown in FIG. 36B, and then the shaft portion 145 is rotated counterclockwise so that the magnetic tape 10 is pinched between the inner surface of the axial hole 143 and the arcuate outer surface of the shaft portion 145 as shown in FIG. 36C. This example is advantageous in that the leader pin is easy to assemble.

[0128] The leading end portion of the magnetic tape 10 may be inserted into the axial hole 143 before the shaft portion 145 is inserted into the axial hole 143.

[0129] In the fifteenth example shown in FIGS. 37 to 39, the leader pin 4 comprises a pin body 114 and a clamp member 116 which is fitted on the pin body 114 to form the main portion 11. The pin body 114 has a shaft portion 115 which is substantially equal in outer diameter to the small diameter portions 12. A protrusion 147 is formed on the outer surface of the shaft portion 115 to extend in the longitudinal direction of the pin body 114 and a pair of short protrusions 147 a for positioning the magnetic tape 10 are formed at the ends of the protrusion 147 to extend in a circumferential direction of the shaft portion 115.

[0130] As shown in FIG. 39, the protrusion 147 is shaped so that the main portion 11 formed when the clamp member 116 is fitted on the shaft portion 115 is substantially circular in cross-section.

[0131] The protrusion 147 facilitates positioning of the leading end of the magnetic tape 10 in the longitudinal direction of the tape 10 and the short protrusions 147 a facilitate positioning of the magnetic tape 10 in the transverse direction thereof.

[0132] In the sixteenth example shown in FIGS. 40, 41A and 41B, a loop of a leader tape 148 is connected to the leading end of the magnetic tape 10 and the pin body 114 is inserted into the loop of the leader tape 148 so that the shaft portion 115 is opposed to the leader tape 148. Then the magnetic tape 10 is pulled leftward as seen in FIG. 40 so that the leader tape 148 is brought into close contact with the shaft portion 115 and then the clamp member 116 is press-fitted on the shaft portion 115 with the leader tape 148 intervening therebetween.

[0133] The loop of the leader tape 148 may be made around the pin body 114 after placing the pin body 114 on the first leader tape. Further the magnetic tape 10 may be connected to the leader pin by way of a loop of a splicing tape in place of the loop of the leader tape.

[0134] The leader tape 148 may be bonded to the magnetic tape 10 by use of splicing tape 149 as shown in FIG. 41A. Otherwise, heat-sensitive adhesive may be applied to the inner surface of the leader tape 148 and the opposite ends of the leader tape 148 may be bonded to opposite sides of the leading end portion of the magnetic tape 10 as shown in FIG. 41B by applying heat to the opposite ends of the leader tape 148 with the leading end portion of the magnetic tape 10 sandwiched therebetween. In this case, the leader tape 148 may be bonded to the shaft portion 115 by the heat-sensitive adhesive, if desired.

[0135] It is possible to use a heat-shrinkable leader tape 148 and fix the leader tape 148 to the shaft portion 115 by heating and shrinking the loop of the leader tape 148 after the shaft portion 115 is inserted into the loop. In this case, the clamp member 116 may be eliminated.

[0136] In this example, even when the leader tape 148 is connected to the magnetic tape 10 by use of a splicing tape 149, the length d of the spliced portion can be short as shown in FIG. 41A, whereby adverse effect of the shoulders formed at the spliced portion can be avoided when the leader pin is drawn into the tape drive system.

[0137] In the case where the clamp member 116 is formed of synthetic resin, there is fear that tape holding strength of the clamp member 116 is weakened due to expansion and/or reduction in coefficient of elasticity of the resin when the leader pin is stored or used under an elevated temperature. When the clamp member 116 is formed of crystalline resin such as polyamide, polyoxymethylene or polybutylene terephthalate and the temperature of the mold is set lower than the normal temperature when molding the clamp member 116 so that the resin becomes low in crystallinity, reduction in the tape holding strength of the clamp member 116 can be avoided since the crystallinity of the resin is increased to shrink the clamp member 16 and the coefficient of elasticity of the clamp member 116 increased as the temperature increases.

[0138] Further when the outer surface of the shaft portion 115 and/or the inner surface of the clamp member 116 is roughened by graining, etching, spark erosion or the like, disengagement of the magnetic tape 10 from the leader pin can be prevented.

[0139] When the surface roughness Rz of the surfaces is too small, the tape holding force becomes poor and when the surface roughness of the surfaces is too large, ejection of the clamp member 116 from the mold becomes difficult, scrapings of resin are produced when the clamp member 116 is press-fitted on the pin body 114 and/or the magnetic tape 10 can be broken. Accordingly the surface roughness Rz is preferably in the range of 0.7 μm≦Rz≦30 μm and more preferably in the range of 1 μm≦Rz<20 μm.

[0140] Further when the clamp member 116 is press-fitted on the shaft portion 115 of the pin body 114 with the magnetic tape 10 intervening therebetween, air can be trapped between the magnetic tape 10 and the clamp member 116 and the magnetic tape 10 is wrinkled. This problem can be overcome by forming a slit or a hole in the clamp member 116 at the center thereof.

[0141] In the examples where the clamp member 116 is press-fitted sideways on the shaft portion 115 with the magnetic tape 10 intervening therebetween out of the examples described above, there is fear that the magnetic tape 10 is broken especially when the magnetic tape 10 is thin. This problem can be overcome by folding the leading end portion of the magnetic tape 10 in two or more as shown in FIGS. 42A to 42C and press-fitting clamp member 116 on the shaft portion 115 with the folded portion 150 of the magnetic tape 10 intervening therebetween. The folded portion 50 also functions as a damper when the magnetic tape 10 is pulled.

[0142] Further it is preferred that the clamp member 116 be provided with a flat portion 116 f on at least one part of the outer surface thereof as shown in FIG. 43. For example, when the clamp member 116 is press-fitted on the pin body 114, the clamp member 116 is held by holding jigs 151 with its slit faced downward above the pin body 114 and the magnetic tape 10 supported on a support 153 and is pressed against the shaft portion 115 by a pusher tool 152.

[0143] Accordingly when the flat portions 116 f are in parallel to the direction of pushing the clamp member 116 by the pusher tool 152, positioning of the clamp member 116 with respect to the holding jigs 151. A flat portion 116 f on the side of the clamp member 116 opposite to the slit limits the direction of pushing the clamp member 116 by the pusher tool 152 and ensures the area at which the pusher tool 152 pushes the clamp member 116. Further when a flat portion 115 f is provided on the pin body 114 at the portion facing the support 153, the pin body 114 can stably supported on the support 153.

[0144] The magnetic tape 10 may be directly bonded to the leader pin by use of hot-melt adhesive tape 154 and a hot pressing tool 155 as shown in FIG. 45. Use of the hot-melt adhesive tape is advantageous in that the adhesive layer can be more uniform in thickness than when adhesive is used and it is not necessary to use solvent.

[0145] It is preferred that the outer peripheral surface of each flange 13 be provided with non-skid treatment such as knurling, diamond knurling and splining. This is for preventing slip of the leader pin when the leader pin is chucked by an assembly jig during assemble of the magnetic tape cartridge or by the tape drawing mechanism of the tape drive system.

[0146] In the example shown in FIG. 46, the outer peripheral surfaces of the flanges 13 are splined as indicated at K.

[0147] It is further preferred that the leader pin be provided with a cutaway portion for determining the angular position of the leader pin in order to facilitate positioning the leader pin when connecting the magnetic tape to the leader pin and when the leader pin is incorporated in the cartridge casing.

[0148] In the example shown in FIG. 47A, the upper flange 13 is provided with a pair of parallel flat surfaces S. The flat surfaces S are parallel to each other and to the direction in which the magnetic tape 20 extends from the leader pin. As shown by the chained line in FIG. 47A, an assembly jig 100 chucks the leader pin at the flat surfaces S, whereby the assembly jig 100 can chuck the leader pin constantly in a predetermined angular position.

[0149] As shown in FIGS. 47B and 47C, the flat surfaces S may be formed only a part of the flange 13 as seen in the direction of thickness of the flange 13.

[0150] It is generally required that the main portion 11 of the leader pin has a predetermined outer diameter when the leader pin is incorporated in the cartridge casing. In some of the preceding examples, this requirement can be met by properly selecting the outer diameter of the clamp member 116. However this requirement may also be met without use of the clamp member.

[0151] That is, in the example shown in FIGS. 48 to 50, the leader pin 4 comprises a shaft portion 115, a pair of inner flanges 132 on opposite ends of the shaft portion 115, a pair of small diameter portions 12 on the outer sides of the inner flanges 132 and a pair of outer flanges 13 on the outer sides of the small diameter portions 12. The inner flanges 132 are substantially equal in outer diameter to the outer flanges 13. The leading end of the magnetic tape 10 is tacked to the outer surface of the shaft portion 115 by adhesive, water or alcohol and the magnetic tape 10 is wound around the shaft portion 115 until the outer diameter of the tape roll 216 becomes substantially equal to that of the inner flanges 132 while applying light tension to the magnetic tape 10. Then the magnetic tape 10 is bonded to the outermost run of the tape roll 216 by adhesive as shown in FIGS. 48 to 50. In FIG. 50, reference numeral 217 denotes adhesive, water or alcohol for tacking the leading end of the magnetic tape 10 to the shaft portion 115 and reference numeral 218 denotes the adhesive for bonding the magnetic tape 10 to the outermost run of the tape roll 216. In this state, the leader pin 4 is incorporated in the cartridge casing.

[0152] In any one of the preceding examples, it is preferred that the leader pin be formed of corrosion resistant material. As the corrosion-resistant material, plastic materials such as aliphatic polyamides (e.g., nylon 6, nylon 66(6,6; 6/6) and the like), aromatic polyamide, polycarbonate, polybutylene terephthalate, polyphenylene sulfide, polymethyl methacrylate, polyoxymethylene, and the like, plastic materials having an imide group such as polyimide, polyamide-imide, polyether-imide and the like, stainless steel materials such as SUS304, SUS306, SUS316, SUS410 and the like may be employed. These materials are also advantageous in that they are hard to magnetize. That is, when the leader pin is magnetized, magnetism of the leader pin can affect the information recorded on the magnetic tape. When the leader pin is to be formed of the aforesaid plastic materials, it is preferred that the plastic materials be reinforced with glass fibers or carbon fibers.

[0153] Further the leader pin may be provided with hard chrome plating.

[0154] As shown in FIG. 51, the leader pin 4 on the leading end of the magnetic tape 10 is held in a recess 228 formed inside the tape outlet opening 2 by a pair of spring members 230 which press the flanges 13 of the leader pin 4 against the inner surface of the recess 228 when the magnetic tape cartridge is not used.

[0155] As shown in FIG. 52, guide surfaces 229 for guiding the leader pin 4 into the recess 228 are formed on the inner surfaces of the upper and lower casing halves la and lb. It is preferred that the peripheral edges of the upper and lower flanges 13 be chamfered so that they can smoothly slide on the guide surfaces 229. The recess 228 has upper and lower inner surfaces which are flat and spaced from each other by a distance substantially equal to the length of the leader pin 4. The guide surfaces 229 are inclined so that they linearly approach each other toward the recess 228. The slide door 3 is slid back and forth across the guide surfaces 229 and the upper and lower faces 3 a of the slide door 3 are inclined to conform to the shape of the guide surfaces 229.

[0156] When the magnetic tape 10 is rewound and the leader pin 4 is retracted into the recess 228, the flanges 13 slide on the upper and lower guide surfaces 229 and the leader pin 4 is successfully retracted into the recess 228 even if the center of the leader pin 4 is shifted from the center of the recess 228.

[0157] Though, in this embodiment, the space between the upper and lower guide surfaces 229 linearly changes, it may change curvilinearly. That is, each guide surface 229 may be curved. In such a case, the upper and lower end faces 3 a of the slide door 3 are shaped to conform to the shape of the guide surfaces 229.

[0158]FIG. 53 shows a modification of the guide surface 229. In this modification, the guide surface 229 is provided with a V-shaped groove 233 which extends from the tape outlet opening 2 to the flat recess 288. The groove 233 is formed over the entire width of the guide surface 299 and becomes shallower toward the recess 228.

[0159] With this arrangement, the flange 13 of the leader pin 4 slides along the center of the guide surface 229 at which the groove 233 is deepest and is smoothly guided to the recess 228 in an erected position.

[0160] In another modification shown in FIG. 54, the guide surface 229 is provided with a V-shaped groove 234 which extends from the tape outlet opening 2 to the flat recess 288 and becomes smaller in width toward the recess 228.

[0161] With this arrangement, the flange 13 of the leader pin 4 slides along the center of the guide surface 229 at which the groove 234 is deepest and as the flange 13 approaches the recess 228, the flange 13 comes to run onto the flat surfaces on opposite sides of the groove 234, whereby the leader pin 4 can be smoothly guided into the recess 228.

[0162] As shown in FIG. 55A and 55B, the guide surface 229 may be provided with V-shaped groove 235 or U-shaped groove 236 only at the middle portion thereof.

[0163] In FIGS. 53, 54, 55A and 55B, reference numeral 237 denotes a sliding groove along which the slide door 3 is slit. The grooves 233 and 234 in the modifications shown in FIGS. 53 and 54 may be U-shaped in cross-section.

[0164] The guide surface and/or the surface of the sliding groove 237 may be subjected to treatment for reducing friction so that the leader pin 4 or the slide door 3 slides more smoothly.

[0165] The treatment may involve, for instance, embossing, application of lubricant such as silicone, or application of a low friction sheet. 

What is claimed is:
 1. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises that the leader pin is provided at its opposite ends with engagement portions which are brought into engagement with a tape drawing mechanism of a recording and reproducing system when the magnetic tape cartridge is loaded in the recording and reproducing system, and the end face of each engagement portion is provided with a recess at which the tape drawing mechanism chucks the leader pin.
 2. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises that the leader pin comprises a pin body which is provided at its opposite ends with engagement portions which are brought into engagement with a tape drawing mechanism of a recording and reproducing system when the magnetic tape cartridge is loaded in the recording and reproducing system, and a clamp member which is provided with a slit extending in the longitudinal direction thereof and is resiliently press-fitted sideways on the pin body with the leading end portion of the magnetic tape intervening therebetween, thereby clamping the leading end portion of the magnetic tape on the leader pin, and that a positioning means which positions the leading end portion of the magnetic tape with respect to the leader pin is provided on at least one of the pin body and the clamp member.
 3. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises that the leader pin comprises a pin body which is provided at its opposite ends with engagement portions which are brought into engagement with a tape drawing mechanism of a recording and reproducing system when the magnetic tape cartridge is loaded in the recording and reproducing system, and a pair of members which are bonded together with the pin body and the leading end portion of the magnetic tape intervening therebetween.
 4. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises that the leader pin is provided with a tape clamp portion which is hinged to the leader pin and resiliently fitted on the leader pin with the leading end portion of the magnetic tape pinched therebetween, thereby clamping the leading end portion of the magnetic tape on the leader pin.
 5. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises that the leader pin is provided with a slit extending in the longitudinal direction thereof and the magnetic tape is clamped on the leader pin with its leading end portion inserted into the slit and held there by a wedge shaped clamp member press-fitted in the slit.
 6. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises that the leader pin is provided with a slit extending in the longitudinal direction thereof and the magnetic tape is wound around the leader pin with its leading end portion inserted into the slit.
 7. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises the leader pin is formed plastic molding with one end portion of a temperature-resistant sheet inserted thereinto and the leading end of the magnetic tape is connected to the other end of the temperature-resistant sheet.
 8. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises that one end of a leader sheet is connected to the leading end of the magnetic tape, the other end of the leader sheet is inserted into a slit formed in the leader pin and an engagement means which connects the leader sheet to the leader pin is provided on the leader sheet and the leader pin.
 9. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises that the leader pin comprises a pin body which is provided with a shaft portion on which the leading end portion of the magnetic tape is attached, a pair of engagement portions which are formed on opposite ends of the shaft portion and brought into engagement with a tape drawing mechanism of a recording and reproducing system when the magnetic tape cartridge is loaded in the recording and reproducing system, a pair of inner flanges formed between the shaft portion and the engagement portions and a pair of outer flanges which are formed on the outer ends of the engagement portions and are removably held in the cartridge casing, and a clamp member which is press-fitted sideways on the pin body with the leading end portion of the magnetic tape intervening therebetween, thereby clamping the leading end portion of the magnetic tape on the leader pin, and that when the distance between the outer surface of the engagement portion and the outer surface of the outer flange is represented by h, the distance between the outer surface of the shaft portion and the outer surface of the inner flange is represented by a, and the distance between the outer surface of the engagement portion and the outer surface of the inner flange is represented by b, at least one of a and b is not larger than 2 h/3.
 10. A magnetic tape cartridge as defined in claim 9 in which the clamp member is provided with an annular recess on each end face thereof and the inner flange on the pin body is received in the annular recess.
 11. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises that the leader pin comprises a pin body which is provided with a shaft portion on which the leading end portion of the magnetic tape is attached, a pair of engagement portions which are formed on opposite ends of the shaft portion and brought into engagement with a tape drawing mechanism of a recording and reproducing system when the magnetic tape cartridge is loaded in the recording and reproducing system, a pair of annular grooves formed between the shaft portion and the engement portions and a pair of outer flanges which are formed on the outer ends of the engagement portions and are removably held in the cartridge casing, and a clamp member which is provided with protrusions on its ends and is press-fitted sideways on the pin body with the protrusions received in the annular grooves and with the leading end portion of the magnetic tape intervening therebetween, thereby clamping the leading end portion of the magnetic tape on the leader pin.
 12. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises that the leader pin comprises a pair of pin halves which are mated with each other with their contact surfaces abutted against each other along a plane including the longitudinal axis of the leader pin, the pin halves being provided with recesses and projections on their contact surfaces so that when the pin halves are mated with each other with their contact surfaces abutted against each other and with one of the pin halve inverted relative to the other, the projections on each pin half is inserted into the recess on the other, and the leading end portion of the magnetic tape is pinched between the pin halves.
 13. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises that the leader pin comprises a hollow cylindrical member provided with an axial hole and a slit which is formed on the outer surface of the cylindrical member to communicate with the axial hole and to extend in the longitudinal direction of the cylindrical member, and a shaft member which is substantially semi-circular in cross-section and is inserted into the axial hole of the cylindrical member to be rotatable therein, the shaft member being first positioned in a position where it permits insertion of the leading end portion of the magnetic tape into the axial hole through the slit and then rotated, after the leading end portion of the magnetic tape is inserted into the axial hole, to a position where it pinches the leading end portion of the magnetic tape together with the inner surface of the axial hole.
 14. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises that the leader pin comprises a pin body which is provided at its opposite ends with engagement portions which are brought into engagement with a tape drawing mechanism of a recording and reproducing system when the magnetic tape cartridge is loaded in the recording and reproducing system, and a clamp member which is provided with a slit extending in the longitudinal direction thereof and is resiliently press-fitted sideways on the pin body with the leading end portion of the magnetic tape intervening therebetween, thereby clamping the leading end portion of the magnetic tape on the leader pin, a protrusion being formed on the outer surface of the pin body to extend in the longitudinal direction of the pin body and to fill the slit of the clamp member when the clamp member is fitted on the pin body.
 15. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises that the leader pin comprises a pin body which is provided at its opposite ends with engagement portions which are brought into engagement with a tape drawing mechanism of a recording and reproducing system when the magnetic tape cartridge is loaded in the recording and reproducing system, and a clamp member which is resiliently press-fitted sideways on the pin body with a loop of a leader tape connected to the leading end portion of the magnetic tape fitted on the pin body, thereby clamping the leader tape on the leader pin.
 16. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises a loop of heat-shrinkable leader tape is connected to the leading end of the magnetic tape and the leading tape is heated after it is fitted on the leader pin so that the loop of the leader tape is shrunken and fixed to the leader pin.
 17. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises that the leader pin comprises a pin body which is provided at its opposite ends with engagement portions which are brought into engagement with a tape drawing mechanism of a recording and reproducing system when the magnetic tape cartridge is loaded in the recording and reproducing system, and a clamp member which is provided with a slit extending in the longitudinal direction thereof and is resiliently press-fitted sideways on the pin body with the leading end portion of the magnetic tape intervening therebetween, thereby clamping the leading end portion of the magnetic tape on the leader pin, a rough surface being provided on the surface of the pin body which is brought into contact with the magnetic tape and/or the surface of the clamp member which is brought into conatct with the magnetic tape.
 18. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises that the leader pin comprises a pin body which is provided at its opposite ends with engagement portions which are brought into engagement with a tape drawing mechanism of a recording and reproducing system when the magnetic tape cartridge is loaded in the recording and reproducing system, and a clamp member which is provided with a slit extending in the longitudinal direction thereof and is resiliently press-fitted sideways on the pin body with the leading end portion of the magnetic tape intervening therebetween, thereby clamping the leading end portion of the magnetic tape on the leader pin, the leading end portion of the magnetic tape clamped by the clamp member being folded.
 19. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises that the leader pin comprises a pin body which is provided at its opposite ends with engagement portions which are brought into engagement with a tape drawing mechanism of a recording and reproducing system when the magnetic tape cartridge is loaded in the recording and reproducing system, and a clamp member which is provided with a slit extending in the longitudinal direction thereof and is resiliently press-fitted sideways on the pin body with the leading end portion of the magnetic tape intervening therebetween, thereby clamping the leading end portion of the magnetic tape on the leader pin, the clamp member being provided with at least one flat portion on the outer surface thereof.
 20. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises that a chucking portion is formed on a part of the leader pin and the chucking portion is provided with an anti-slip treatment.
 21. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises that a cutaway portion is formed on the leader pin for determining the angular position of the leader pin with respect to the position on the leader pin in which the magnetic tape is fixed to the leader pin.
 22. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises that the leader pin is formed of a corrosion-resistant material.
 23. A magnetic tape cartridge as defined in claim 22 in which the corrosion-resistant material is plastic.
 24. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin fixed to the leading end portion of the magnetic tape, wherein the improvement comprises that the leader pin comprises a pin body comprises a pin body which is provided with a shaft portion around which the leading end portion of the magnetic tape is wound and a pair of engagement portions which are formed on opposite ends of the shaft portion and brought into engagement with a tape drawing mechanism of a recording and reproducing system when the magnetic tape cartridge is loaded in the recording and reproducing system, the magnetic tape being connected to the pin body wound around the shaft portion to form a roll having a predetermined diameter.
 25. A magnetic tape cartridge comprising a cartridge casing formed of upper and lower casing halves, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation and a leader pin which is fixed to the leading end portion of the magnetic tape, the ends of the leader pin being removably held in a recess formed inside a tape outlet opening in the cartridge casing, wherein the improvement comprises that the recess has upper and lower inner surfaces which are flat and spaced from each other by a distance substantially equal to the length of the leader pin, and upper and lower guide surfaces are formed in the cartridge casing to extend from the upper and lower inner surfaces of the recess to the tape outlet opening so that the distance between the upper and lower guide surfaces becomes larger toward the tape outlet opening.
 26. A magnetic tape cartridge as defined in claim 25 in which a slide door for opening and closing the tape outlet opening is provided to be slid across the upper and lower guide surfaces and the upper and lower end faces of the slide door are shaped to conform to the shape of the upper and lower guide surfaces.
 27. A magnetic tape cartridge as defined in claim 25 in which each of the guide surfaces is provided with a recess extending along the path along which the leader pin is drawn into the recess.
 28. A magnetic tape cartridge as defined in claim 25 in which the guide surfaces are subjected to friction reduction treatment. 